The present disclosure relates to a battery having a plurality of battery modules which are arranged in battery strings and can be selectively activated or deactivated by means of driving, the battery module voltage of a respective battery module contributing to an output voltage of the corresponding battery string of the battery in the activated state. The disclosure also relates to an associated method for operating the battery. In addition, the disclosure relates to a vehicle having the battery.
It is becoming apparent that new batteries, on which very high demands with regard to reliability, safety, performance and service life will be imposed, will be increasingly used in future in stationary applications, for example wind power installations, in vehicles, for example hybrid and electric vehicles, and in the consumer sector, for example in laptops and mobile telephones. Batteries having lithium ion technology, in particular, are suitable for such tasks. They are distinguished, inter alia, by a high energy density and an extremely low self-discharge.
Previous disclosures by the applicant presented methods concerning how a lithium ion battery can be expediently subdivided into modules which are then connected to form individual strings which then directly drive an electric motor. An example of a modular battery is disclosed in the document DE 10 2010 027 864 A1. The corresponding principle is explained in more detail by way of example below using FIG. 1.
According to FIG. 1, a battery 100 has a plurality of battery strings 101 with battery modules 102. Each battery module 102 has one or more battery cells 103, only one battery cell 103 of which is illustrated in the drawing for each battery module 102. Each battery module 102 also respectively has two switches 104, 105, a respective battery module 102 being able to be activated or deactivated depending on the switching position of the switches 104, 105. In the activated state, the battery module voltage of the respective connected or activated battery module 102 contributes to an output voltage of the corresponding battery string 101, which output voltage is then available at a connection 106. In contrast, in the deactivated state, the battery module 102 is decoupled from the battery string 101 and is bridged in an electrically conductive manner.
An advantage of the arrangement according to FIG. 1 is that a battery voltage can thus be set in a variable manner. For example, with sufficiently fine division of the battery strings 101 into a multiplicity of battery modules 102 and with appropriate driving, a sinusoidal profile of the battery voltage can be set at the terminals 106, which profile has a phase shift. This makes it possible to drive a (three-phase) electric motor 107, even without the need for a special interposed inverter.
Previous disclosures by the applicant also presented a battery, in which the individual battery modules are connected to a DC/DC converter. FIG. 2 illustrates such an arrangement by way of example, the circuits of the battery modules 102 shown each being supplemented with a secondary subcircuit 207 of the DC/DC converter. The DC/DC converter is preferably in the form of a flyback converter. The secondary subcircuits 207 each have a diode 201 and a secondary coil 202. The primary-side subcircuit 206 of the battery 200 has a primary coil 204 and a switch 205. DC-isolation between the battery modules 202 and the primary-side subcircuit 206 can also be effected using the coil core 203. As an advantage of the circuit topology shown, it is possible, for example, to charge the battery modules 202 from the 12-V power supply system or, depending on the configuration of the DC/DC converter, from the 220-V domestic power supply system. However, the circuit topology from FIG. 2 results in a high wiring complexity and therefore high costs since each battery module 202 must be wired to a separate secondary coil 202 on the DC/DC converter. In addition, although it is possible to carry out active balancing between the battery modules 102 and individual battery strings 101 in the battery 200 during operation by connecting the individual battery modules 102 for different periods of time depending on their performance during the production of the desired AC output voltages, such a method cannot be used at a standstill or during charging, for example.